Protein S, free

1. Check the expiration date on the label of the blue top vacutainer before drawing the patient.

2. For blood collection in a sodium citrate blue top, the tube must be filled to above the Minimum Fill Indicator on the tube. It is crucial to wait and allow the tube to stop filling before removing it from the needle.

3. With use of a butterfly needle, draw about 1 cc using a separate blue top to remove air from tubing, discard the first tube and then draw a second blue top tube filled to the full extent of the vacuum.

4. Tubes should not be filled past the Maximum Fill dashed line by either using a syringe or removing the tube cap.

Draw only before institution of oral anticoagulant therapy or after a stable therapeutic regimen has been established.

Container type

Blue top filled to full extent of vacuum

Amount to Collect

2.7 mL blood

Sample type

Citrated plasma

Preferred volume

1 mL plasma

Min. Volume

0.5 mL plasma

UCSF Rejection Criteria

Samples collected in outdated blue top vacutainer. Over-filled or under-filled tubes may be rejected

Processing notes

This is the typical test that should be ordered when a request for Protein S is received unless it explicitly states 'Activity'. If 'activity' is specified order PSACT.

There is no published pediatric reference range for Free Protein S antigen, which generally parallels the level of Total Protein S antigen, and from which the pediatric (< 6 months old) reference ranges given below are derived.

Full Term Infant

Day 1

Day 5

Day 30

Day 90

Day 180

12-60%

22-78%

33-93%

54-118%

55-119%

From: Andrew M et al. Development of the Human Coagulation System in the Full Term Infant. Blood. 1987, 70: 165- 172

Healthy Premature Infant

Day 1

Day 5

Day 30

Day 90

Day 180

14-38%

13-61%

22-90%

40-112%

44-120%

From: Andrew M, et al. Development of the Human Coagulation System in the Healthy Premature Infant. Blood November 1988, 72(5): 1651-1657.

Synonyms

Free Protein S antigen

Turn around times

2-4 weeks

Additional information

A normal level does not exclude the possibility of an immunologically intact but dysfunctional protein.